The p-rank $\epsilon$-conjecture on class groups is true for towers of p-extensions

Abstract

Let p$\ge$2 be a given prime number. We prove, for any number field kappa and any integer e$\ge$1, the p-rank $\epsilon$-conjecture, on the p-class groups Cl\_F, for the family F\_kappa^p^e of towers F/kappa built as successive degree p cyclic extensions (without any other Galois conditions) such that F/kappa be of degree p^e, namely: #(Cl\_F[p])<<\_{kappa,p^e,$\epsilon$}($\sqrt$D\_F)^$\epsilon$, where D\_F is the absolute value of the discriminant (Theorem 3.6) and, more generally, #(Cl\_F[p^r])<<\_{kappa,p^e,$\epsilon$}($\sqrt$D\_F)^$\epsilon$, for any r$\ge$1 fixed. This Note generalizes the case of the family F\_Q^p (Genus theory and $\epsilon$-conjectures on p-class groups, J. Number Theory 207, 423--459 (2020)), whose techniques appear to be "universal" for all relative degree p cyclic extensions and use the Montgomery--Vaughan result on prime numbers. Then we prove, for F\_kappa^p^e, the p-rank $\epsilon$-conjecture on the cohomology groups H^2(G\_F,Z\_p) of Galois p-ramification theory over F (Theorem 4.3) and for some other classical finite p-invariants of F, as the Hilbert kernels and the logarithmic class groups.